Compile, for android 6.0, adb for "device-on-target"

Question

For some reason, on android 6.0, the building of adb for 'device-on-target' was removed from the Android.mk.
That was, actually, very useful to have. you can see the diff between the 6.0 mk and the 5.0 mk:
6.0 mk - https://github.com/android/platform_system_core/blob/master/adb/Android.mk
5.0 mk - https://github.com/android/platform_system_core/blob/lollipop-release/adb/Android.mk
(scroll to the end of the mk)
Does any one here knows how to compile the adb for device-on-targed on android 6.0?